Oct 22, 2009
Pinhole irradiation patterns nanostructures in just a few nanoseconds
Quasi percolated nanostructured silver thin films are the starting material to produce ordered patterns. Samples were prepared and characterized in the Physics and Chemistry Departments of Universidad Autónoma Metropolitana Iztapalapa (UAMI) in Mexico City. The synthesis was performed using pulsed laser ablation and samples were subsequently irradiated through a 60 µm pinhole with an Nd-YAG laser emitting in the UV.
The diffracted pattern was precisely imprinted in the film in the form of concentric circles of spheroidal nanoparticles having dimensions between 5 and 100 nm. The geometrical characterization of the nanostructures and nanoparticles was performed by transmission electron microscopy and atomic force microscopy. Furthermore the observed effects can be explained using Fresnel diffraction theory, suggesting that precise patterning engineering can be performed through the control of spatial parameters such as the pinhole diameter and the distance from the mask to the sample.
Fast and simple technique
The whole process takes place in a few nanoseconds, generating simultaneously micron and submicron patterning in the surface of the film. The deposition in a vacuum chamber and patterning in air of the samples are realized with the same laser.
"The various applications we have in mind include high-density storage media and patterned surface enhanced Raman spectroscopy (SERS) substrates. Patterning of larger surfaces could be achieved by controlling the mask and by using piezoelectric devices to move the sample," Emmanuel Haro-Poniatowski told nanotechweb.org. "From a fundamental point of view, it is very important to understand the thermodynamic mechanisms that determine the final size of the nanoparticles. This information will help us to design strategies to control the size distribution of the nanoparticles".
The researchers presented their work in the journal Nanotechnology.
About the author
The work was performed during the sabbatical stay of Prof. Juan Carlos Alonso-Huitrón (Universidad Nacional Autónoma de México) at the Physics Department of Universidad Autónoma Metropolitana Iztapalapa (UAMI) and continues as a co-operative study between researchers in the two institutions. Prof. Nikola Batina is head of the Nanotechnology and Molecular Engineering Laboratory, Prof. Emmanuel Haro-Poniatowski is head of the Physics Department, Cristina Acosta-García is a graduate student in experimental biology and Carlos Acosta-Zepeda is an undergraduate student in physics. This work was partially financed by the Consejo Nacional de Ciencia y Tecnología (CONACYT) of Mexico.